Method for enriching ores and the like

ABSTRACT

In a method for enriching ores or like materials the components of which have simultaneously different contents and mechanical strength values, the ore is submitted to a controlled crushing causing the softer fraction of the ore to be ground to a predetermined particle size controlled by discharging the softer component as it is reduced to the predetermined particle size. The predetermined particle size is determined experimentally and is dependent on the differential friability of the material to be processed. The self-crushing operation is performed in a drum of which the screening elements consist of detachable, interchangeable quadrants providing the necessary passages for the softer component.

United States Patent [191 Saunal 1 Mar. 12, 1974 METHOD FOR ENRICHING ORES AND THE LIKE [75] Inventor: Robert Saunal, Paris, France 221 Filed: Oct. 4, 1972 21 App]. No.: 297,034

Related US. Application Data [60] Continuation of Ser. No. 114,765, Feb. 12, 1971, abandoned, which is a division of Ser. No. 752,215, Aug. 13, 1968, abandoned.

[30] Foreign Application Priority Data Aug. 21, 1967 France 67.118416 [56] References Cited UNITED STATES PATENTS Claes 241/34 3,078,049 2/1963 Hardinge 241/26 Primary ExaminerGranville Y. Custer, Jr. Attorney, Agent, or Firm--Wender0th, Lind & Ponack [5 7] ABSTRACT In a method for enriching ores or like materials the components of which have simultaneously different contents and mechanical strength values, the ore is submitted to a controlled crushing causing the softer fraction of the ore to be ground to a predetermined particle size controlled by discharging the softer component as it is reduced to the predetermined particle size. The predetermined particle size is determined experimentally and is dependent on the'differential friability of the material to be processed. The selfcrushing operation is performed in a drum of which the screening elements consist of detachable, interchangeable quadrants providing the necessary passages for the softer component.

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ATTORNEYS 1 METHOD FOR ENRICHING ORES AND THE LIKE This application is a continuation of my application Ser. No. 114,765, filed Feb. 12, 197l, now abandoned which is in turn a division of my application Ser. No. 752,215, filed Aug. 13, 1968, entitled Method And Device For Enriching Ores And The Like, now abandoned.

BACKGROUND OF THE INVENTION I This invention relates to a method for enriching or concentrating ores or the like the components of which have simultaneously different contents and mechanical strength values. Examples of such ores are the various types of ores produced in the Lorraine District in France.

It is known that the various ores found throughout the world vary considerably as far as their contents of pure metal and/or other valuable components are concerned. Thus, certain iron ores are considered as lowiron content ores because their Fe contents range from about to about percent, as contrasted with rich ores containing more than 60 percent Fe. It has therefore been attempted for many years to enrich lean ores, or to concentrate the iron therein, in order to make them commercially competitive with high-iron content ores.

To this end, many ore enriching methods have been proposed.

These known methods, notably in the case of the above-mentioned Lorraine iron ore, involve grinding the ore to a fine mesh size (of the order of 0.5 mm or less) and subsequently applying a treatment consisting either of a magnetic sorting process (high-current magnetic separation), or even a preliminary roasting (magnetizing roasting followed by a low-current magnetic separation).

However, in many cases the cost of these treatments is relatively high and therefore they are seldom employed, especially in the case of the above-mentioned lean iron ores from the Lorraine district.

Another process aiming at enriching lean ores of which the component, elements are characterised by different contents and mechanical strength values, involves self-crushing the ore under controlled conditions so as to leave the harder components unaltered and permit the separate recovery of these harder fractions from the softer fractions thus divided into a finer particle size.

However, these methods are objectionable in that they do not afford an accurate control of the particles of fragments eventually collected.

As a rule, these known methods are characterised by the dual common drawback that for a given ore it is not possible to determine the best possible apparatus characteristics capable of giving a product having optimum contents and size, and that these methods do not permit a strict control of the cost of the corresponding operation thereof.

OBJECTS AND BRIEF DESCRIPTION OF THE INVENTION In view of the foregoing, it is the principal object of this invention to provide a method for enriching or concentrating ores or the like the components of which have simultaneously differnet contents and mechanical strength values. This method adequately meets practical operational requirements, notably in that the specific size to which the softer components are to be reduced can be determined with a considerable degree of precision.

To this end, the present invention provides a method of enriching ores or the like, the components of which have simultaneously different contents and mechanical strength values, this method being characterised in that the ores or the like are submitted to a controlled selfcrushing operation causing the softer component of the ores to be ground to a predetermined particle size controlled by discharging the softer component as it is reduced to such predetermined particle size.

According to an advantageous form of the method of this invention the predetermined output particle dimension of the softer component is subordinate to the differential friability of the treated material, i.e. the

ore.

The term differential friability as used in the present specification and claims means the ability of the ore to separate into two constituents, one relatively hard and the other relatively soft, and each of which has simultaneously different contents of the metal or other valuable component with which it is desired to enrich the ore. The differences in the contents of the metal or the like in the two constituents result from the differences in friability thereof. This new realization makes it possible to define for a valuable raw material a new measurable property. The differential friability may be preliminarily experimentally determined by subjecting samples of a given ore to controlled self-crushing operations wherein different maximum particle sizes of the more friable material are separated and analyzed. The operation having a maximum particle size resulting in a desired content of the valuable material in the more friable material is then selected for operational treatment of the ore. For each ore or other valuable raw material which consists of parts having different friabilities, it is thus possible to determine the content of the valuable component of these parts and, as a result of this determination, define for the ore the differential friability thereof.

In its specific application to iron ores from the Lorraine district in France, which consist essentially of limestone blocks distributed in a mass of softer ore having a substantially higher iron content (35 to 45 percent) than the limestone blocks 15 to 25 percent), the ore enriching method of this invention consists in submitting the ores to a controlled self-crushing operation whereby the softer constituent is crushed to an optimum particle dimension determined by the experimentally determined differential friability of the ore. The softer constituent, the iron content of which ranges from about 35 to about 40 percent, is discharged immediately, while the harder constituents remain in the unground condition in the crushing apparatus from which they. are subsequently discharged separately.

The method constituting the subject-matter of this invention is also applicable, of course, to ores wherein the constituent having the higher metal content is the harder constituent, the enriching process being carried out in a manner similar to that described above.

The method of this invention makes it possible to accurately control the size of the softer constituent in order to reduce it to its optimum particle size with due consideration to the metal content and the percentage by weight of the two constituents desired to be achieved, and to economical aspects of the process. This size control is obtained by simply discharging the softer constituent immediately as it reaches the predetermined size. This discharge is also advantageous in that it avoids any over-crushing or over-grinding of the fine particles which would obviously take place if these fine particles remained in the controlled self-crushing cycle, a particularly important feature for the subsequent use of the finished products. Moreover, due to the provisions of the present invention, the presence of a thick layer of fine ground or over-ground products which would obviously interfere with the continuation of the self-crushing process while unduly increasing the cost of the operation is safely avoided.

An apparatus suitable for carrying out the method of the invention is characterised essentially in that it comprises a plurality of screening elements consisting of quadrant-shaped members mounted in a rotatably driven drum. The quadrants are formed with discharge apertures for discharging the softer crushed fractions of the treated ore. The dimensions of the apertures may vary gradually from one quadrant to another in the direction of circulation of the ore. The quadrants may be interchangeable with one another and may be detachable and removable from outside the apparatus. The apertures formed in the quadrants for discharging the softer crushed fractions of the product may be adjustable in size.

The drum in which the screening elements are mounted may consist of a cylindrical assembly of longitudinal beams made rigid with transverse reinforcing rings, the gap left by the mutual arrangement of the beams and rings being calculated for receiving the screening quadrants. The structure constituting the roraty drum carries on its outer periphery points or the like made from a relatively hard material for preventing clogging in the zone where the screened product is discharged. The drum in which the screening elements are mounted is adapted to be disassembled and may be in turn mounted on a supporting frame the inclination of which can be varied from to The drum is housed in a casing of asymmetrical construction which results in improved evacuation of the crushed material, with due consideration for its path controlled notably by the velocity and the direction of rotation of the apparatus. The harder materials are discharged separately from the discharge of the softer crushed materials by means of extraction blades or the like. The ore to be treated is fed to the apparatus by means of a frustoconical inlet section having an adjustable inlet passage. The supply of ore to the apparatus is adjusted by fitting a replaceable collar or like member as a function of the size of the ore.

BRIEF-DESCRIPTION OF THE DRAWINGS In order to afford a clearer understanding of this invention and of the manner in which the same may be carried out in practice, reference will now be made to the accompanying drawings in which:

FIG. 1 is a longitudinal section showing an apparatus constructed to carry out the method of the invention;

FIG. 2 is a cross-sectional view showing the feed end of the apparatus where the material to be treated is introduced;

FIG. 3 is a fragmentary perspective illustration of a specific form of a screening element;

FIG. 4 is another perspective illustration of a different form of a screening element; and

FIG. 5 is an exploded view showing the self-crushing drum.

DETAILED DESCRIPTION OF THE INVENTION Although the following description refers to the specific forms illustrated in the drawings it will be readily understood that these are merely given by way of example and should not be-constructed as limiting the scope of the invention as set fourth in the appended claims.

A controlled self-crushing apparatus may comprise a rotary drum 1 having mounted therein a plurality of quadrants 2 which constitute the screening elements of the apparatus. This drum 1 is rotatably mounted in a supporting frame structure 3. The material to be treated is introduced into the apparatus through a frusto-conical inlet section 4. The drum 1 in which the screening quadrants 2 are mounted is rotatably driven from an electric motor 5.

Each screening quadrant 2 comprises for example either a plurality of radial strips 6 (FIG. 3) or perforated bottom plates 7 (FIG. 4). The gaps between the radial strips 6 of the bottom of the quadrants 2 are calculated to permit the passage only of the predetermined optimum particle size of the softer material to be treated during the self-crushing process of this invention. The various quadrants 2 juxtaposed throughout the length of the drum 1 may have the same or different dimensions, and the passage formed therein for screening the softer fraction of the treated material may have different dimensions or cross-sectional passage areas from one quadrant to the adjacent quadrant in the direction of flow of the material. Moreover, as the quadrants 2 are detachable and can be removed from the exterior of the apparatus, the choice of the dimensions of the quadrants and/or their passages can be varied at will by simply substituting some or all of the quadrants as a function of the specific properties of the material to be treated. The particular arrangement of screening elements consisting of quadrants of the type described and illustrated herein by way of example affords a more complete treatment of the material and therefore the obtaining of a treated material the rate of enrichment of which is considerably greater that the rates hitherto obtained with methods and devices of the prior art.

The structure of the drum 1 advantageously consists on the one hand of a set of parallel longitudingal beams 9 disposed at spaced intervals about the drum axis along the generatrices of a cylinder, and on the other hand of reinforcing rings 10 joining beams 9 and im parting to the drum structure an inherent rigidity independent of the screening elements. The beams 9 carry on their outer peripheral surface spaced points 15 (see FIG. 5) of hardened metal for the purpose of preventing the clogging of the zone receiving the screened material.

Practical considerations and tests prove that it may be advantageous to provide for a drum structure made of several sections adapted to be easily disassembled, for example in the longitudinal or axial direction (FIG. 5 particularly when it is contemplated to operate the ore enriching apparatus on the mining site proper, especially underground. The dimensions of the apertures left between the component elements of the drum structure, namely the beams 9 and reinforcing rings 10,

correspond to the size of the various quadrant 2 to be mounted therein.

Whereas the softer constituent of the treated material is discharged at its predetermined optimum particle size, as this size is attained during the drum rotation, through the passages formed between the quadrant elements 6 or 7, the harder constituent is discharged at the end of the enriching process through the discharge or outlet opening 8, advantageously with the assistance of extraction blades 12 or the like.

The rotary drum 1, in which the rigid screening elements consist advantageously of quadrants 2, is housed in a casing 13, and this assembly is advantageously mounted in a suitable manner on a supporting frame 3. The casing 13 is mounted or possibly constructed asymmetrically in relation to the drum 1, with a view to ensure a better discharge of the crushed material towards a transfer mechanism, for example in the form of a conveyor belt 14 disposed beneath the bottom of the apparatus.

The inclination of the controlled self-crushing apparatus can be varied with respect to the horizontal by connecting the supporting frame 3 to a suitable device such as a screwram (not shown).

The member for supplying material to be treated to the apparatus may advantageously consist of a frustoconical section 4 wherein the dimensions of the inlet passage are made adjustable by means of any suitable device, for instance by using replaceable and interchangeable collars selected as a function of the initial or input dimensions of the material to be treated.

The ore enrichment of the material treated in the apparatus, by separating the softer constituents from the harder constituents, thereby concentrating the amount of the desirable material in one of these constituents, i.e. either the harder or the softer constituent, is achieved in the abovedescribed apparatus by performing a controlled self-crushing of the material as a consequence of the rotation of the apparatus.

The dimensions of the apparatus, particularly by the overall length and diameter thereof, the dimensions of the passages formed both in the screening elements 2 and in the drum 1, the treatment time, the degree of inclination of the apparatus to the horizontal, are determined as a function of the nature of the ore, notably the degree of relative hardness of the ore components (i.e. the softer and harder components) which determine the degree of differential friability of the ore to be treated.

The Lorraine limestone ores are formed of two very distinct portions. Limestone lumps, having an iron content of from 20 to 25 percent, are located in the midst of a rich ore, the iron content of which is about 40 percent. There exists therefore in the ore a heterogeneity involving a difference of cohesion, the limestone lumps being more resistant.

The exploration of Lorraine limestone ores illustrates this phenomenon, since after crushing, screening of the ore to a maximum particle size of mm gives a fraction having a particle size of from 0 to 10 mm which is clearly enriched in iron.

Meanwhile, an examination of the product obtained by placing in operation known crushing processes show that they do not obtain the desired separation, and the differences in content of iron in the products obtained is less then when employing the present method. Therefore, prior art processes profit only slightly from the heterogeneity of the ore. However, by employing the process according to the invention of an automatic crushing operation which constitutes a more manageable operation than the operations proposed in the prior art, it is possible to more fully profit from the heterogeneity of the ore. The process of the invention furthermore allows the evacuation of the valuable products more carefully in accordance with their obtention without additional crushing and allows a suitable dimension for feeding the agglomeration.

The following examples describing the practical application of the method of the present invention refer more particularly to the application of this invention to the processing of low-iron content ore, notable from the Lorraine district in France, but it will be readily understood by those conversant with the art that the Examples should not be construed as limiting the invention.

In these Examples the tests were conducted by using a pilot-apparatus constructed according to the teachings of this invention which, however, should not be considered as limiting the scope of the invention, notably from the dual point of view of the size and mode of operation commercial apparatus to be subsequently constructed.

EXAMPLE 1 In a self-crushing apparatus constructed according to the above description, 1,820 kilograms of a particular ungraded ore (particle size ranging from 0 to 200 mm) having the chemical composition shown in line 3 of the following Table l were treated.

First, an ore sample was subjected to an experimental self-crushing operation wherein the more friable constituent was reduced to a maximum particle size of 10 mm. The iron content and total weight of the more fn'able constituent are indicated in line 1 of Table 11.

Then a similar ore sample was subjected to an operation wherein the more friable constituent was reduced to a maximum particle size of 20 mm. The results of the analysis of this more friable constituent are shown in line 2 of Table II.

Finally, a similar ore sample was subjected to an .operation wherein the more friable constituent was reduced to a particle size above 20 mm. The results of the analysis of this more friable constituent are shown in line 3 of Table II and line 1 of Table I.

It is to be understood that other operations could be performed on similar ore samples wherein the maximum particle size of the more friable constituent is set at further difierent values. The particle size is of course varied by varying the screening quadrants.

After conducting these experimental operations and studying the analysis thereof as shown in Tables 1 and II, it is possible to make a judgement, based on cost,

TABLE I I Analysis F Granulomctric Weight, Percent contents, fractions, mm. kg. l .w. c CaO SiO 09.0 percent time, etc., as to the maiii mum particle size parameter desirable in the operational treatment of a given batch of ore. This desirable size parameter is thus selected, and the treatment of the batch of ore is thereafter conducted by reducing the more friable constituent to such maximum particle size. friable of said constituents,

I WM has A W V 2. simultaneously passing said loosened more fria- EXAMPLE 2 ble constituent through openings of a predeter- Furthermore, in the experimental processing of sammined size to separate particles of said more friaples of a given batch of ore, the treatment time may be ble constituent of said predetermined size from varied, and the resulting product is analyzed each time. 3, anal zin the content of said desired comu a a I I y g I Thus, additional valuable information lS obtained in ponent in one of said thus separated con- 2 connection with the various results that can be eil stituents, V V pected by using a continuous commercial operation. 4. repeating above steps (1), (2), and (3) as The fragmentary results obtained during one of these desired by subjecting further examples of said tests are listed in Table ill hereinafter. ore to controlled self-crushing operations while H A IKB LE'EF 7 Analysis of the 0-10 mm. fraction of the rich prod.

Weight F SlOz, CaO, A1203, Feyleld, Weight, Fe, Fe yield, Treatment time Product percent percent percent percent percent percent percent percent percent Rich roduct 60.7 37.2 6.8 13.9 3 "lR jeci s 39. a 23. 2 5.6 28. 7 0 2 3 1o 33:; 2:2 Q3 53. 7 37. s 63.3 Initial produet 100 31. 8 6. 3 19. 7

From the preceding description it will be readily ap simultaneously passing said thus loosened parent that whatever the forms of application and more friable constituent through openings of mode of operation adopted, the present invention prodifferent predetermined sizes, thereby obtainvides a method for enriching ores or the like the comi g different quantities of said more friable ponents of which have simultaneously different conconstituents, tents and $tren gth the P 5. selecting the predetermined particle size of method being characterised m comparison with hlthsaid more friable constituent resulting in a em) know? methods mtendfifd for the sfmle by suitable concentration of said desired comthe essential fact of affording a considerable ennch- 45 ponem, thereby indicating Said degree of ment of the treated lean ores at a relat vely low cost. differential friability and As empha slz ed by the above descnptlon thls f b. a second stage of operationally subjecting said ore not hmted y the mqdes 9 operatlon to a controlled self-crushing operation and causing deFCHbed paftlcularly f f Smce F said more friable constituent to be ground to said prises all modifications and variations that Will occur to Selected particle Size and Separated from said less those skilled in the art, without departing from the spirit and scope of the invention.

1 claim:

1. A method for concentrating a desired component friable constituent as soon as it is reduced to said selected particle size.

7 i. Kih ethod as claimed in claim l further comprisof an ore having at least two constituents, each of said 5 5 ing varying periods of time each of said samples of said constituents having a different degree of friability and different concentration, said method comprising:

a. a first stage of experimentally determining the degree of differential friability between the constituore are subjected to said self-crushing operation. 

2. simultaneously passing said loosened more friable constituent through openings of a predetermined size to separate particles of said more friable constituent of said predetermined size from said less friable constituent,
 2. A method as claimed in claim 1, further comprising varying periods of time each of said samples of said ore are subjected to said self-crushing operation.
 3. analyzing the content of said desired component in one of said thus separated constituents,
 4. repeating above steps (1), (2), and (3) as desired by subjecting further examples of said ore to controlled self-crushing operations while simultaneously passing said thus loosened more friable constituent through openings of different predetermined sizes, thereby obtaining different quantities of said more friable constituents,
 5. selecting the predetermined particle size of said more friable constituent resulting in a suitable concentration of said desired component, thereby indicating said degree of differential friability, and b. a seCond stage of operationally subjecting said ore to a controlled self-crushing operation and causing said more friable constituent to be ground to said selected particle size and separated from said less friable constituent as soon as it is reduced to said selected particle size. 